Nerve injury is a major risk during a surgery. Minimally invasive surgical procedures with small incisions limit direct visualization of the targeted site and therefore reinforce the need of improved techniques for neurostimulation and neuromonitoring.
Intra-operative neuromonitoring (IONM) has been performed for a long time by the neurophysiologist practitioners and well known techniques like motor evoked potentials (MEP), transcranial motor evoked potentials (TcMEP), train of four (TOF), somatosensory evoked potentials (SSEP) and free-run electromyography (EMG) have been proven. These techniques help the IONM specialist to assess the nervous system of the patient during the surgery and more particularly give information on the health of targeted nerves in the proximity of the surgical site. However, these techniques have limitations and don't offer an immediate feedback on potential nerve damage that may occurred during specific actions performed by the surgeon. Usually, electrified probes are used by the surgeon to send stimulation current into the patient's tissues. The stimulation current flows through the tissues to a reference electrode placed in the near proximity of the surgical site. The amplitude of the current sent is set sufficiently high in order to reach and depolarize the nerves running into the stimulated tissues and potentials will be evoked in the related muscles. EMG signals or mechanical movements will be recorded on the neuromonitoring system via electrodes placed on or in the patient's muscles. In a typical method of nerve locating, the stimulation current is then lower and more probing is done towards the identified nerve until evoked potentials in the muscles are recorded again. This loop may be repeated several times until the stimulation current is down to an amplitude where the nerve depolarizes only when the probe is in contact with it. Since the IONM specialist doesn't have direct access and visualization of the surgical site, it's difficult for him to trigger and set the appropriate nerve stimuli in order to monitor the right parameter.
Surgical gloves are personal protection equipment designed to provide comfort and tactile sensitivity while protecting clinicians and patients during operating procedures in an operating room environment. The primary purpose of surgical gloves is to act as a protective barrier for surgeons and nurses to prevent possible transmission of diseases or pathogens during procedures while working with surgical instruments. Similar to medical examination glove, surgical glove standards are governed by the Food and Drug Administration (FDA) within the United States and other regulated entities around the world. Mechanical and biocompatible properties must follow the minimal requirements published in the applicable standards. Since the majority of surgical gloves are still made from natural rubber, latex allergy awareness has open ways for additional materials to be introduced in the manufacturing of surgical gloves. Many latex-free materials like polychloroprene, nitrile, vinyl or polyisoprene (synthetic rubber) are available. All surgical gloves are sterilized and package sealed in pairs for single use. The sterilization of surgical gloves is standard as surgical procedures often involve open wound operation. In contrast to medical exam gloves, surgical gloves are form fitted meaning every pair contains one glove shaped for the left hand and one glove shaped for the right hand. This is to ensure the highest level of comfort, tactile feeling and to help reduce fatigue from long surgical procedures. In contrast to medical examination gloves, surgical glove are sized in order to provide a better fitting glove which will be available for every surgeon.
In the U.S. Pat. No. 4,510,939; Brenman et al. describe the invention of a means for applying electrical stimuli to living tissue. This method uses a surgical glove on which electrodes and electrical conductors are mounted on the external surface of the glove with adhesive materials. At least one stimuli electrode and a second reference electrode are placed on the finger of the glove. This invention is only suitable for stimulating by palpation some localized internal cavities of the body but cannot be used for intra-operative neurostimulation since the electrical current flows from the stimuli electrode on the glove to the reference electrode on the glove. This keeps the electrical path local to the finger and would only depolarize a nerve if touching it with the glove or in near proximity. Despite the fact that the stimuli electrode and the reference electrode are too close to each other, Brenman's glove would need to be connected to a neuromonitoring system that can record electrical responses of the muscles and where stimulation currents can be adjusted in relation to those responses in order to perform nerve health assessment and nerve localization. Further, Brenman's invention would not be suitable for surgical glove since the adhesive material used for affixing the electrodes and electrical conductors would affect the mechanical strength and elongation properties of the glove in such a way that it would not pass the required standards for surgical gloves. Moreover, during many surgeries, areas that need to be stimulated are not accessible by palpation with fingers.
In the U.S. Pat. No. 3,845,771 from Vise and in the U.S. Pat. No. 6,551,312 from Zhang et al.; both Vise and Zhang described a method of transmitting electrical energy to wireless instruments through surgical gloves having electrical conductors. These inventions are limited to transmitting electrical energy to electrosurgical devices as electrocautery or electro-coagulation devices. Electrocautery or electro-coagulation requires currents in a range of 500 to 700 mA in order to produce localized heat when the current is concentrated in a small surface of contact. Therefore, Vise and Zhang's gloves require larger and thicker electrical contact pads in order to transmit the high currents needed to the instrument without producing heat. Having larger and thick pads on the glove is not suitable for surgical gloves where the surgeon needs to have high tactile feeling through the glove. Electrocautery or electro-coagulation usually operates at frequencies between 100 KHz and 5 MHz in order to minimize effects of muscle contraction or nerve stimulation. It is well known that it is impossible to perform neuromonitoring during electrosurgery due to the fact that electrosurgery uses high frequencies, including radiofrequencies, and high voltages to cut through and coagulate tissues, and this causes important noise perturbation of the neuromonitoring signals. Further, Vise and Zhang need to control the activation of the electrosurgical source of current by the use of a mechanical switch either on the instrument or in between the electrosurgical source and the glove in order to switch off the electrical current that flows through the electrical conductors of the glove and avoid important risks of electrocution or injury to the patient if the surgeon inadvertently touches the body of the patient. This is opposite to the present invention where the main advantage is to always send electrical stimulations through instruments without having to manually activate it.
The Spitznagle discloses, in the U.S. Pat. No. 6,567,990, electromyography (EMG) electrodes mounted on the examination gloves and used for measuring the electrical currents generated by muscles contraction. The glove of this invention is only used for sensing EMG signals which resolve from muscle movements and not to stimulate the muscle. Further, similar to the '939 glove of Brenman, there are two electrodes on the finger, one being active and the other being indifferent or the ground reference.
In the U.S. Pat. No. 7,207,949 of Miles et al., U.S. Pat. No. 6,466,817 of Kaula et al., U.S. Pat. No. 7,470,236 of Kelleher et al., these inventors disclosed a surgical access system equipped with electrodes to send stimulation currents through the instruments into the patient's body and a stand-alone neuromonitoring system for detecting and mapping the nervous system. This system's instruments are all connected to the stimulator through a wired electrical connector. It has been observed that the surgical team either inadvertently forgets to connect the electrical connector to the instrument being used or the surgeon switches between instruments rapidly and there is no time to interrupt the surgical procedure. As a result, no electrical stimulation is sent through the instruments and therefore, it is difficult if not impossible to monitor the nerve location.
In the U.S. Pat. No. 5,067,478, Berlant disclose a structure and method of manufacturing an electrode glove for applying electro-massage. This method requires the use of two gloves that are partially covered with an electrically conductive layer. To close the electrical circuit, the stimulating current flows from one glove into the patient's skin then back to the second glove. This invention is only suitable for stimulating large areas of the skin but cannot be used for intra-operative neurostimulation since the electrical current flows from one glove to the other glove. This would produce a large flow of current circulating through the skin that would not depolarize a nerve or would not be localized enough to give valuable information in order to monitor the nerve location or assess on the nerve health. Further, Berlant describes a manufacturing technique to make an electrical layer on a glove by dipping a former in a natural rubber compound and then over-dipping it in a natural rubber loaded with a non-metallic conductive material like carbon black. This technique would work if the thickness of the conductive layer is large enough and the concentration of the non-metallic conductive material dispersed in the natural rubber compound is high enough to reach the percolation point. However, it has been demonstrated and tested that the loading of non-metallic material necessary to make an electrically conductive layer having a resistivity of 2000 Ohms or lower is so high that the mechanical properties of the conductive layer like the elongation and the tensile strength would be weak and the conductivity would be lost when the glove is stretched. This technique would not be suitable to make surgical gloves that are designed to fit tightly a surgeon's hand and therefore need to be stretched during donning. The weaker mechanical properties of Berlant's conductive layer would not meet the standard requirements for a surgical glove. It has also been demonstrated that a high concentration of carbon black dispersed in rubber would leave black traces of carbon on all objects that are in contact with the glove, which would not be acceptable in a surgical environment.
In the U.S. Pat. No. 6,584,359, Motoi discloses stimulation gloves for resolving wrinkling, sagging and such of skin conditions. Similar to the '478 glove of Berlant, two gloves are used to generate a flow of alternative current square-waves through large areas of the skin. Even if this way of stimulation is useful in providing a cosmetic effect on the skin, it would not depolarize nerves and gives valuable information for neuromonitoring purposes.
In the U.S. Pat. No. 6,904,614, Yamazaki et al. disclose a pulse health appliance with a glove that comprises a pair of electrodes in order to electrically stimulate an outside portion of the human body. This method uses a glove on which patch electrodes and electrical conductors are made of conductive woven cloth mounted on the external surface of the glove. At least one stimuli electrode and a second reference electrode are placed on the glove. This invention is only suitable for stimulating by palpation some localized external region of the body but cannot be used for intra-operative neurostimulation since the electrical current flows from the stimuli electrode on the glove to the reference electrode on the glove. This would produce a large flow of current circulating through the skin that would not depolarize a nerve or would not be localized enough to give valuable information in order to monitor the nerve location or assess on the nerve health.
In the U.S. Pat. No. 7,128,741, Isaacson et al. describe a method of transmitting electrical energy to wireless electrosurgical instruments through an electrode pad upon which the surgeon stands and through an electrical path disposed in the surgical gown and gloves. This invention is limited to transmitting electrical energy to electrosurgical devices as electrocautery or electro-coagulation devices. It is well known that it is difficult, if not impossible, to perform neuromonitoring during electrosurgery due to the fact that electrosurgery uses high frequencies, including radiofrequencies, and high voltages to cut through and coagulate tissues, and this causes important noise perturbation of the neuromonitoring signals. It would be extremely difficult to transmit neurostimulation signals through an electrode pad since the electrical signals have significantly smaller amplitude and undesirable artifacts would be generated and would affect the measurements. Further, Isaacson tries to control the activation or the operating modes of the electrosurgical device by wirelessly communicating signals from the instrument to the electrosurgical generator using a battery powered transmitter placed inside the electrosurgical instrument. As discussed above for Vise's '771 and Zhang's '312 patents, transmitting electrosurgical currents through the gown and glove presents an important risk of electrocution or injury to the patient if the surgeon inadvertently touches the body of the patient when using the electrocautery device. Another limitation of Isaacson's invention is that a battery assembled inside the electrosurgical instrument is required in order to supply power to the wireless transmitter which controls the electrosurgical generator. It is well known that steam sterilizable batteries are expensive and don't last long.
In the U.S. Pat. No. 6,141,643, Harmon describes a glove that has at least two electrical pads, one being positioned on the fingertip and the other being positioned on the palm portion. Both electrical pads are operatively connected to an output connector. Making a contact between the finger pad and the palm pad generates a signal. This invention relates to generating electrical signals for communication purposes using electrical contacts on a non-surgical glove and therefore far away from the surgical glove used for neurostimulation purposes described in the present invention. Further, Harmon's invention requires that at least one electrical pad and a second reference electrical pad are placed on the glove in order for an electrical current to flow through when both electrical pads are in contact.
In the U.S. published patent application 2010/0010367, Foley et al. disclose a method of adhering a small electrode on the fingertip of a standard surgical glove for locally stimulating tissues during anterior spine surgery and allowing IONM equipment to determine the health status and/or the location of the nerves. The lead wire that connects the electrode to the IONM system needs to be adhered or attached along the glove and the arm of the surgeon. Despite the fact that this electrode can send stimulation current by palpation into the body for IONM purpose, it is not suitable for transmitting stimulation currents to wireless instruments. Moreover, the electrode and the lead wire are add-ons to the surgical glove that affect the tactile feeling of the surgeon at the locations where the electrode and the lead wire are attached. It will also reduce the freedom of movement of the surgeon's hand during the procedure and may present an important risk of grabbing soft tissues when the surgeon's hand is inside the wound. It is well known that adhering something on a glove made out of cured rubber is very difficult and even more when the rubber is in contact with blood and body fluids. Therefore, there is a high probability that the electrode or the lead wire become loose after a short period of use and requires to being reattached or replaced and then increase the time of the procedure. A partially loosened lead wire may also involuntary grab instruments or other things that could be in the way during movements of the surgeon's arm. Moreover, during many surgeries, areas that need to be stimulated are not accessible by palpation with a finger and there is a need to use instruments.
What is needed is a neuromonitoring system that has a glove with a single stimulating electrode and an independent reference electrode in a spaced apart relationship on the glove at a surgical site in such a fashion that the electrical current flows from the glove to the reference electrode through the patient body.
Further, there is a need to quickly interconnect multiple wireless surgical instruments with an electrical source of stimulation to insure that the surgeon is constantly stimulating the surgical site to allow neuromonitoring to occur.
Still further, there is a need for a neuromonitoring system that has a glove with a single stimulating electrode for rapidly holding and electrically connecting to a wireless surgical instrument.
Yet still further, there is a need for a neuromonitoring system that has a glove with a single stimulating electrode for rapidly holding and electrically connecting to a wireless surgical instrument, where the stimulating electrode and its connection path are manufactured thin enough and completely integrated in the glove to not affect the mechanical properties of the glove and not change the tactile feeling of the surgeon.
Still yet further, there is a need for a neuromonitoring system that has a glove with a single stimulating electrode for rapidly holding and electrically connecting to a wireless surgical instrument, where the addition of the stimulating electrode, its connection path and the surgical instrument have an electrical resistivity below 2000 Ohms and where the surgical glove has mechanical and biocompatibility properties that meet the required standards for surgical gloves.
Further still yet, there is a need for a neuromonitoring system that has a glove for transmitting a low frequency, low voltage electrical stimulation that will not harm the tissue if the glove inadvertently touches the patient.
Still yet further, there is a need for a kit of electrically conductive surgical instrumentation and access tools that wirelessly work with a glove stimulator.
Further still yet, there is a need for a kit of electrically conductive surgical instrumentation and access tools that wirelessly work with a glove stimulator where the IONM specialist can remotely control the stimulation input.